Question

The Water Department checks the city water supply on a regular basis for contaminants such as trihalomethanes (THMs). The Water Department takes 200
samples and estimates that the concentration of THMs in your drinking water is 3 ppb (parts per billion), with a standard deviation of 0.3 ppb.
Assuming the samples were random and unbiased how much confidencr can you have in this data?

A. 95% confident the average concentration of PCBs in the water supply is between 2.4 ppb and 3.6 ppb.
B. 68% confident the average concentration of PCBs in the water supply is between 2.9 ppb and 3.1 ppb..

Answer 1

C. 97% confident the average concentration of PCBs in the water supply is between 2.6 ppb and 3.8 ppb.
D. 99.7% confident the average concentration of PCBs in the water supply is between 2.7 ppb and 3.3 ppb.

Answer 2

looks like this requires previous information that was already given to you to get an answer, is there any more info to this question?

Answer 3

No this is all the info it gave me

Answer 4

Do you have to do this by hand or can you use a program like statcrunch?

Answer 5

By hand

Answer 6

Unless the othwr one is easier

Answer 7

I was only here for help so my answers may be poor.

You can either do it in the program statcrunch using STAT > Z STATS > ONE SAMPLE > WITH SUMMARY

or by hand with this
https://onlinecourses.science.psu.edu/stat200/node/48

Answer 8

Hopefully somebody who is better at stats will come along.

Answer 9

I got the answer it was A if anyone needed it